An example of a conventional small lamp using a wedge base bulb of the prior art is described in Japanese Examined Utility Model Publication No. 53-1825. Specifically, this example of the prior art is a small interior lamp for automobile use equipped with a housing, a lens located in the opening of the housing, a holder attached to the housing, and a wedge base bulb supported in the holder. The holder includes a holder body, formed by a bent U-shaped conductive metal strip, and an attachment piece integrated into a single unit with the holder body and extending in the opposite direction from the U-shaped conductive metal strip. A center piece and right and left side pieces are provided in opposition at selected intervals protruding from the top and bottom of the engaging indentation. The U-shaped portion of the holder body is clamped between the center piece and both the side pieces by fitting into the engaging indentation. In such a manner, therefore, the holder body is formed in the housing. In this state, the attachment piece of the holder body is fixed in the housing together with a conductive strip for connection. Since the prior art described above comprises an interior lamp by directly forming the holder portion of a wedge base bulb in the side edge of a hole in an interior lamp housing, and directly inserting a connector into a housing base, there is a tendency for the bulb to become loose due to thermal deformation of the base caused by accumulation of heat in the bulb holder. Such looseness is particularly acute when bulbs of roughly 5 W or more are used. Moreover, contact resistance increases in riveted portions resulting in a further accelerated increase in looseness, ultimately leading the interior lamp not being operational.
In addition, the prior art is also disadvantageous since the peripheral members of the connector, such as the bulb holder, have a relatively complex structure. Such a complex structure therefore typically requires manual assembly and connection thereby making it unsuitable for automated wiring and assembly systems. Furthermore, no light beam reflecting plate is provided in the prior art bulb holder, thereby promoting low light utilization efficiency.